1. Field of the Invention
The present invention relates to an improvement in a camera with a non-TTL type finder operatively coupled with a photo-taking optical system.
2. Description of the Related Art
A coupled range finder is well known as a typical example of conventional non-TTL type finder operatively coupled with a photo-taking optical system (photo-taking lens).
The finder of this type is structured, for example as shown in FIG. 9 or 10, such that a feed mechanism of a photo-taking optical system is interlocked by a proper coupling mechanism with a deflector of a coincidence type range finder to complete a focusing operation of the photo-taking optical system when double images of a subject coincide with each other.
A coupled range finder as shown in FIG. 9 is arranged such that a photo-taking optical system (not shown) is fed out by a translation helicoid mechanism (not shown). The deflector is a concave lens 101, which is one of the simplest arrangements. This arrangement can be used either in case of an interchangeable photo-taking optical system or in case of a photo-taking optical system fixedly mounted in a camera.
In the above example, the concave lens 101 as the deflector is mounted at an appropriate position on a swing lever 103, which may swing about a support shaft 102. A free end 104 of the swing lever 103 is in contact with a member 105 directly connected to the translation helicoid mechanism through a biasing force of a biasing spring 106.
The swing lever 103 rotates about the support shaft 102 with a motion of the translation helicoid mechanism in a direction of arrow A upon focusing of the photo-taking optical system. The rotation of the swing lever 103 deviates the concave lens 101 by an amount depending upon the motion of the translation helicoid mechanism in a direction perpendicular to the finder optical axis, whereby achieving a coincidence of double images of a subject.
Another coupled range finder as shown in FIG. 10 is an example in which the deflector is a rotation mirror 111. This arrangement can also be used either in case of the interchangeable photo-taking optical system or in case of the photo-taking optical system fixedly mounted in a camera.
In this example, the rotation mirror 111 as the deflector is mounted at a rotation center of a first lever 113, which swings about a support shaft 112. A free end of the first lever 113 is in contact through a proper gap adjusting mechanism 114 with a contact member 116a provided at an end of a second lever 116, which swings about a support shaft 115.
Transmitted through an interlocking pin 117 to the other end 116b of the second lever 116 is a motion of the translation helicoid mechanism in a direction of arrow A' upon focusing of the photo-taking optical system. The motion of the translation helicoid mechanism is reduced through the second lever 116 to be transmitted to the first lever 113. Then the rotation mirror 111 is rotated by an angle corresponding to the motion of the translation helicoid mechanism, whereby achieving a coincidence of double images of a subject.
Another example of the non-TTL finder is known to display whether a deviation direction of focusing dial manually operated by a user is coincident with a distance measurement result obtained by a so-called active AF (auto-focus).
The coupled range finders have such complex arrangements including a number of constituent members, which need a strict dimension accuracy management, presenting a big problem in structure, in production, and in cost.
The non-TTL type finder using the latter active AF always displays a difference between the distance measurement of the active AF and an indication distance of the focusing dial. Thus, the continuous distance measurement must be carried out, which extremely consumes a power of a battery, presenting a big problem in use.